A typical medical eye dropper dispenses single drops which have large volumes, typically about 50 μL. However, since the human eye can typically retain only 7 μL of fluid on the corneal surface at a time, larger volume results in overflow and loss of part of the medication from the eye surface. In addition, a large volume of a single drop, such as 30 or 50 μL, causes a blinking reflex which removes majority of the fluid from the cornea, and inconvenience which leads to poor compliance. U.S. Pat. Pub. 2012/0070467 A1 (incorporated herein by reference in its entirety) describes a droplet generating device for drug delivery to the eye which comprises a piezoelectric actuated droplets generator for delivering small droplets to the eye. This device operates on the principle of nebulizers which use a vibrating plate with multiple apertures to generate aerosol. Such ejector mechanisms are integrally coupled to a fluid reservoir which is periodically refilled by the user. Refilling, however, carries the risk of bacterial contamination and the risk of ocular infection. Generally, drug filling, particularly for ophthalmic use, must be processed in tightly controlled aseptic environment which is not available to the user. Another problem associated with the aerosol delivery as described in the prior art is the user ability to direct the aerosol stream to the surface of the eye. Any misalignment of the dispensing device with the eye will result is inaccurate dosing.
The present invention provides a devices for ejecting therapeutic fluid to surface of the eye or to the conjunctival tissue. The device advantageously utilizes a disposable sterile drug ampoule which can be attached to and detached from a piezoelectric actuator, thereby eliminating the need of refilling and mitigating the possibility of bacterial contamination and providing a cost effective approach reusing the piezoelectric actuator for further operation. The invention further provides a delivery of a single stream and a mechanism to align the stream to the eye prior to actuation to assure convenient and precise dosing. Surprisingly, it has been found that delivery of a single stream imparts lesser impact on the eye and is therefore is more convenient to use when compared to delivery of a mist or a distribution of small droplets which has the same accumulated volume. Unlike a mist or spray, a single stream can be precisely oriented to target a specific location on the surface of the eye or the conjunctival tissue. This characteristic is largely attributed to the aerodynamic behavior of the stream. Specifically, delivery of a mist generally produces a turbulence which causes divergence of the droplet from the target while a stream pierces through the air and reach the target area more precisely.